NSF Young Investigator

NSF 青年研究员

• 批准号: 9457083
• 负责人: Wesley Burghardt
• 金额: $ 29.75万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-09-15 至 2001-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9457083&HistoricalAwards=false
• 关键词: NSF; Young; Investigator

ABSTRACT CTS-9457083 Northwestern University P.I.: Wesley Burghardt The central theme of research in my group at Northwestern in the relationship between flow-induced microscopic structural changes in complex fluids, the resulting mechanical rheological behavior behavior, and further, the consequences of nonlinear rheology in more complex fluid mechanical problems. Under NYI support, we will pursue three projects, (i) Flow-induced alignment in block copolymer solutions. Ordered block copolymers are characterized by complexity at two structural levels. Molecular relaxations are reflected in viscoelastic behavior. However, the self-assembly of the polymers into ordered microstructures (such as lamellae) renders both structure and rheological properties highly anisotropic. We will use flow birefringence to study the development of macroscopic alignment under flow, coupled with mechanical testing to study how bulk rheological behavior is affected by the average orientation state. (ii) Constitutive instabilities in highly entangled polymers. We will investigate two classes of materials where the constitutive behavior has been proposed to be subject to an unstable nonmonotonic dependence of stress on deformation. Highly entangled polymer solutions will be studied in step strain, while so called living polymers (micellar surfactant solutions) will be studied in steady shear flow. In both cases, we will utilize optical approaches developed in our laboratory for studying the complete stress tensor using the stress-optical rule. (iii) Non-newtonian fluid mechanics. Experimental studies will be conducted on well-characterized viscoelastic polymer solutions in complex geometries. These efforts are directed towards developing an experimental database with which to test numerical simulations of viscoelastic flow, and discriminate among competing constitutive models.

摘要CTS-9457083西北大学P.I.： 韦斯利·伯格哈特 我在西北大学的研究小组的中心主题是复杂流体中流动引起的微观结构变化之间的关系，由此产生的机械流变行为，以及更复杂的流体力学问题中非线性流变学的后果。 在NYI的支持下，我们将开展三个项目，（i）嵌段共聚物溶液中的流动诱导排列。 有序嵌段共聚物的特征在于在两个结构水平上的复杂性。 分子弛豫反映在粘弹性行为中。 然而，聚合物的自组装成有序的微结构（如层状结构），使结构和流变性能高度各向异性。 我们将使用流动双折射来研究流动下宏观取向的发展，结合机械测试来研究平均取向状态如何影响体流变行为。 (ii)高度缠结聚合物的本构不稳定性。 我们将研究两类材料，其中本构行为被认为是受不稳定的非单调应力变形的依赖。 高度缠结的聚合物溶液将在阶跃应变中进行研究，而所谓的活性聚合物（胶束表面活性剂溶液）将在稳态剪切流中进行研究。 在这两种情况下，我们将利用我们实验室开发的光学方法，使用应力光学规则研究完整的应力张量。 (iii)非牛顿流体力学 实验研究将在复杂几何形状的粘弹性聚合物溶液上进行。 这些努力是针对开发一个实验数据库，测试粘弹性流动的数值模拟，并区分竞争本构模型。